Agree with Greenish, it's an opposed check. It really depends on how much you choose to max your Hide skill. You really have to have an opponent with an equally high Spot skill or some other form of detecting you to be pinpointed. It's really quite good.
The key thing is to figure out how to move 20' as a swift action and still maintain a +16 BAB. Add Rapid Shot and Haste/Speed and you're up to 6 attacks/round with skirmish. Splitting makes it 12 arrows.